Reddish or brownish seaweed that has enlarged curls or "hooks" at the ends of some branches, allowing it to twine around other seaweeds.
Found on intertidal and shallow subtidal reef flats, tidepools, and rocky benches
Tends to grow on other large seaweeds such as Sargassum (limu kala)
May be free floating is shallow waters
Introduced from Florida to Kaneohe Bay in 1974 for aquaculture research to produce carrageenan
Harm:
Spreads mainly by fragmentation: the "hooks" anchor the hookweed to other seaweed or the reef bottom. Wave action breaks off most of the hookweed, which drifts until it is able to latch onto another location. Even the smallest hooks will grow back until waves break it off again. Not yet observed to produce spores.
Grows faster and shades out coral and other seaweeds, changing reef ecosystem. Small pieces can increase its weight 200% in one week
Large amounts of hookweed wash ashore and decompose at some beaches. The large amounts of the seaweed, along with the smell and flies, decreases beach use and property value
Drifting rafts of seaweed deter ocean use in some areas
In Hawaii:
Kauai: Present at Prince Kuhio Beach and Salt Pond Beach
Oahu: Present in large numbers at some locations such as Kahala, Waikiki, Ala Moana, Kahe and Makaha
Maui: Present in large amounts on many windward and leeward reefs. On some reefs in West Maui and Kihei, hookweed covers 80% of the reef
Molokai: Found at Kaunakakai, Kupepe, and other areas
Lanai: Presence/absence is unknown
Kahoolawe: Presence/absence is unknown
Big Island: Not known to be present at this time
hookweed has recently been found spreading on near-pristine reefs of Mokumanamana (Necker Island) in the Northwestern Hawaiian Islands
